Drafting board straight edge assembly

ABSTRACT

A straight edge assembly, for cord mounting on a drafting board utilizing pulley block units located at the ends of the assembly for stringing the cord thereon. The pulley block units at each end of the straight edge assembly are releasably engaged therewith and may be conveniently dismantled for cord restringing without using tools.

United States Patent Adair et al. July 1, 1975 [54] DRAFTING BOARDSTRAIGHT EDGE 2,275.25] 3/1942 De Lisie 33/80 ASSEMBLY FOREIGN PATENTSOR APPLICATIONS (75] Inventors: William A. Adair, Des Plain s; 1,303.49!8/]962 France 33/30 Richard F. Pollowy, Schaumburg, 604.0[0 6/1948United Kingdom 33/80 both of III. 661MB) 4/1965 Belgium 33/80 [73]Assigneez Teledyne, Inc., Los Angeles, Calif. Primary Examiner Harry N.Hamian [22] Filed: Mar. ll, 1974 21 Appl. No.: 449,958 ABSTRACT Astraight edge assembly, for cord mounting on a s 21 US. Cl. 33/80drafiing ward utilizing Pulley block "nits located at 5| Int. Cl B43]:3/02 the ends of the assembly for Stringing the cord [58] Field ofSearch 33/80, 81 thereon The Pulley block units at each end of thestraight edge assembly are releasably engaged there- [56] ReferencesCited with and may be conveniently dismantled for cord re- UNITED STATESPATENTS stringing without using tools.

l,658.683 2/1928 Jacob 33/80 3 Claims, 9 Drawing Figures DRAFTING BOARDSTRAIGHT EDGE ASSEMBLY BACKGROUND OF THE INVENTION This inventionrelates to a drafting board straight edge assembly. and particularly toinnovations and improvements in a straight edge assembly for cordmounting to a drafting board. More specifically. the invention relatesto novel pulley block units located at the ends of said straight edgeassembly through which the mounting cord runs and which can bedismantled and removed from said straight edge for cord re-stringingpurposes without the use of tools.

Heretofore. straight edges in general use which have been cord mountedto a drafting board by pulley means located at each end of the assemblyhave not been dismantleable without use of tools. The usual method hasbeen to use screws to join pieces making up the straight edge assembly.Also. end covers. or caps usually adjacent the pulley means. have beenattached to the straight edge by use of screws.

The pulley means attached to said end covers usually are located eitherinside a channel running lengthwise through said straight edge or on theside of the drafting board opposite that on which the straight edge islocated and immediately therebeneath. In either case. pulley means arelocated in as small a space as practically possible and as close to thestraight edge or drafting board as attainable so that the mechanism isnot pulled. jerked. banged or torn. from the drafting board because itmay be protruding therefrom. In either case. access to pulley wheels orsheaves is difficult because of space limitations. Therefore.dismantling the straight edge in order to replace a worn mounting cord,replace portions of the straight edge. recover the drafting board. orother purposes has required the use of tools. most likely at least ascrew driver, to gain access to the pulley means to sheaves.

The present invention allows disassembly of the straight edge withoutusing tools, by joining portions of the straight edge permanently withdouble faced adhesive tape and utilizing end covers or caps includingpulley means. The caps are frictionally retained but slidablydisengageable from the straight edge body by gripping said pulley blockunit and pulling laterally away from the straight edge body. Reassemblyof the straight edge is readily accomplished.

It is therefore an object of this invention to provide a straight edgeassembly which may be conveniently assembled and disassembled manuallywithout use of tools.

Another object of the invention is in the provision of a pulley blockunit located at each end and partly inside a straight edge which is cordmounted to a drafting board and is manually releasably engageable withsaid straight edge.

Other objects. features and advantages of the invention will be apparentfrom the following detailed disclosure taken in conjunction with theaccompanying drawings. wherein like reference numerals refer to likeparts. in which:

FIG. 1 is a perspective of a drafting board having a straight edgeassembly cord mounted thereto with the straight edge body partiallybroken away to show a pulley block unit located at the end of thestraight edge;

FIG. 2 is a stringing diagram of the cord by which the straight edgeassembly of FIG. 1 is mounted upon the drafting board;

HO. 3 is an enlarged plan view of one end of the straight edge assemblyof FIG. 1 inverted with a pulley block unit shown partially withdrawnfrom the straight edge channel in which the unit is slidably mounted;

FIG. 4 is a cross section taken along line 44 of FIG. 3 showing thechannel located inside the straight edge;

FIG. 5 is a top plan view of one of the pulley block units of thestraight edge assembly shown in FIG. 1;

FIG. 6 is a bottom plan view of one of the pulley block units.

FIG. 7 is a side elevational view partially in vertical of one of thesheaves in the pulley block units;

FIG. 8 is an end view of one of the pulley block units; and

FIG. 9 is a side view of one of the pulley block units.

Referring now to the drawings and particularly to FIG. 1, a draftingboard is shown having a straight edge assembly 11 mounted thereon bymeans of cord 12 which is fastened to the drafting board 10 at clamp 13.guided by clips l4-14a and pinched and restrained by retainers 15-15a.Straight edge assembly 11 includes a body 18 which is permanentlyassembled having an edge portion 19 made of transparent material, agrasping portion 20, and pulley block units 2l21a located at oppositeends of said body 18.

in FIG. 2 the cord stringing diagram shows the conventional relationshipof cord 12 to the drafting board 10 and the straight edge assembly 11.Cord 12, shown with arrows added thereto for diagraming purposes only,is strung as follows. First, the cord is clamped medially in clamp 13and each side is positioned around a guide clip 14-1412 and along a sideof drafting board 10. Then each cord end passes into straight edgeassembly 11 at pulley unit blocks 2l-21a and around sheave 2424a. Midwaythrough the assembly the cords cross over one another and each endpasses around a second pulley 2626a and down an opposite side ofdrafting board 10 where it is restrained in pinching retainer 15-1501.

Referring to FIG. 3 wherein an end portion of straight edge body 18 isshown turned upside down. one end of the cord 12 enters pulley blockunit 21 at end cap portion 30 through an end cap passageway 31. passesover pulley 24 mounted in the sheave mounting portion 32 and outof thepulley block unit into the body 18 through recess 33 also located insheave mounting portion 32. The other end of cord 12 follows a reversepath. in through recess 33, around sheave 26a, and out passageway 31a.

As is conventional, the cord mounting of said straight edge assembly issuch that cord length remains taut and constant when the straight edgeassembly 11 is moved vertically on drafting board 10. The cross overstringing relationship insures the biasing of straight edge assembly 11at the same reference angle to drafting board 10 wherever said assembly11 is moved up or down on said drafting board 10.

FIG. 4 shows the spatial relationship between edge portion 19, graspingportion 20, the mounting therebetween. and the C-channel 36 into whichthe sheave mounting portion 32 of the pulley block units 21-210 areplaced. Edge portion 19 is a rectangular strip of transparent materialsuch as acrylic plastic. Grasping portion 20 is a modified C-channelwhich may be made of extruded aluminum, steel, plastic or wood. Theinturned free ends 37, 38 of grasping portion 20 are mounted permanentlyto edge portion 19 by means of strips of double faced adhesive tape39-39 made of a compressible sponge-like material having adhesives onboth sides thereof. The different coefficients of expansion of graspingportion 20 and edge portion 19 are compensated for by the flexibility ofdouble faced edged adhesive tape 39-39. Also shown in FIG 4 is a drylubricant tape 40 applied on the bottom of edge portion 19. The bottomexposed surface of dry lubricant tape 40 has a low coefficient offriction and cases movement of straight edge assembly 11 across the topof drafting board 10. Also, the slight thickness of dry lubricant tape40 raises edge portion 19 from the drafting board slightly reducing thepossibility of capillary action smudges on drawing medium mounted on theboard as an ink line is being drawn along the edge of straight edgeportion 19. FIG, 4 shows the cross section shape of channel 36. lt isthis channel into which sheave mounting portions 32 of pulley blockunits 21-210 fit and are frictionally retained so as to be slidablyremovable therefrom. The outer shape and dimensions of grasping portion20 are approximately the same as the shape and outer dimensions of endcap por tion 30.

The details of construction of the pulley block units 2l-2l0 will now bedescribed in connection with FIGS. -9. Referring to FIG. 5 the outsidesurface 43 of end cap portion 30 is preferably of a rough or nonsmoothtexture providing gripping means facilitating removal of pulley blockunit 21-210 from straight edge body 18. As shown, sheave mountingportion 32 has a generally planar top surface 44 and generally planarside surfaces 45-45 except for nubs or detents 46 which protrude fromside surfaces 45-45. Top surface 44, side planar surfaces 45-45. andbottom surfaces 47-47 have outside dimensions slightly smaller than thecorresponding interior dimensions of grasping portion channel 36. Inthis embodiment, nubs or detents 46 are provided to give a propersliding fit for sheave mounting portion 32 in grasping portion C-channel36. Sheave mounting portion 32 slides into the C-channel until end capportion shoulder 50 engages the inner shoulder of grasping portion 20.Inner shoulder 51 is indented from the end of assembly 11 approximatelythe thickness of end cap portion 30. End cap portion 30 then fits in theindented portion when pulley block unit 21-210 is in place. In FIG, 8the C-shape ofend cap portion shoulder 50 is shown.

Turning now to FIG. 6, end cap portion passageways 31-310 and sheavemounting portion recess 33 are shown along with sheaves 24 and 26a. Cord12 moves in and out of pulley block unit 21 through said passageways31-310 and said recess 33. Sheaves 24, 24a, 26 and 260 are identical andare shown in enlarged partially sectioned form in FIGv 7. The sheave isa circular disk having a spindle mounting 52 through the center of saidsheave from one side to the other and a groove 53 running along thecenter of the circumference of said sheave. The sheave also has anintegrally formed spacer hub 54 which prevents movement of the sheaveaxially on spindle 55-550 located in sheave mounting portion 32. Itshould be noted that there is no retainer other than the bottom sidewall 57 of channel 36 which retains sheaves 24, 240, 26, and 260 on thespindles 55-550. Also shown in FIG. 6 is cord guide 58 which is locatedin both sheave mounting portion 32 and end cap portion 30. Cord guide 58is curved immediately adjacent each sheave outer circumferential surfacein the area where cord 12 is located in groove 53. Wall 58 prevents cord12 from leaving groove 53 by covering the top of the groove 53.

In operation, each end of cord 12 is placed at an opposite end ofchannel 36, moved through channel 36. and out the opposite end thereofOne method of performing this function is to place a small weight oneach end of cord 12 while holding straight edge body 18 vertically anddropping the weighted end into and through channel 36. Body 18 is theninverted and the operation repeated using the other end of cord 12. Withone portion of cord 12 going in and another portion of cord 12 comingout each end of body 18, those two portions are placed in sheaves 24, 26and 240, 260, respectively, and the sheaves placed on their respectivespindles 55 and 550. Pulley block units 21-210 are then slidably movedinto installed position with sheave mounting portion 32 inside C-channel36. Thereafter, the two loose cord ends are placed through and retainedby pinching retainers 15-150 at the bottom side edges of board 10.

It should be noted that cross over cord mounting causes inward cordpressure on pulleys 24, 240, 26, 260 toward the center of straight edgeassembly 11. This causes pulley block units 21-210 to be maintained inplace with sheave mounting portion 32 inside C- channel 36 and preventssaid units 21-210 from wandering out of installed position.

In this embodiment, pulley block units 21-210 and sheaves 24-240,26-260. are made of molded plastic. It can be appreciated that othersuitable materials may be utilized without detracting from the scope ofthe invention. It can also be appreciated that while, in thisembodiment, the open end of spindles 55-550, face downward and sheaves24-240, 26-260 are mounted from the bottom that the mounting could bereversed, i.e., mounting from the top, without detracting from the scopeof the invention. Also, it is possible that sheaves 24 and and 260 or240 and 26 could be placed vertically on one spindle S5 and perform thesame function as in the disclosed invention.

We claim:

1. in a straight edge assembly for cord mounting on a drafting board theimprovement comprising a permanently assembled body including an edgeproviding portion and a grasping portion, and a pulley block unitlocated at each end of said assembly which is manually removable andreplaceable without the use of tools, each said pulley block unitincluding an integrally formed pulley block and at least one sheavemounted therein, said block having an end cap portion for covering atleast a part of the end of said body, a sheave mounting portion adjacentsaid end cap portion including a spindle on which said sheave is mountedand retained in place by said contiguous body part, a recess throughwhich said mounting cord passes. and means for frictionally retainingeach said pulley block unit to a contiguous body part at the end of saidassembly and allowing releasable sliding engagement therebetweenincluding a nub extending from an outside surface of said portion whichfrictionally engages said contiguous body part.

2. The improvement of claim 1 wherein said end cap portion furthercomprises, gripping means thereon to facilitate removal thereof fromsaid body portion. a shoulder at the juncture of said end cap and saidsheave mounting portions. said shoulder having the outer di mensions ofsaid body adjacent thereto and inner dimensions of said sheave mountingportion and said end cap portion having at least one passageway thereinfor traversal of a mounting cord therethrough 3. In a straight edgeassembly for mounting on a drafting board by a cord fastened mediate itsends to said board. said assembly including a body having an edgeportion and a downwardly-facing C-channel shaped grasping portion thefree ends of which channel are permanently attached to said edgeportion. the improvement comprising. an integrally formed pulley blockunit located at and partly inside each end of said body which ismanually removable and replaceable without the use of tools. each saidpulley block unit including an end cap portion. a sheave mountingportion attached thereto. and a pair of sheaves mounted side by sidetherein. said end cap portion having outside dimensions correspondingapproximately to the cross sectional outside dimensions of said graspingportion, gripping means for facilitating lateral manual removal of saidunit from said assembly. a pair of passageways therein for the traversalof said cord therethrough. and a shoulder at the juncture of saidmarginal portion and said sheave mounting portion having the outsidedimensions of said body adjacent thereto and the inside dimensions ofsaid sheave mounting portion. said shoulder limiting the travel of saidpulley block unit in said body channel. said sheave mounting portionhaving outside cross sectional dimensions not appreciably greater thanthe corresponding inside dimensions of said channel in said body andfrictionally retained therein. a pair of spindles each having a sheaverotatably mounted thereon. said spindles being retained in place by saidcontiguous body part. a cord retaining shoulder on said mounting portionaround said sheave preventing said cord from disengaging a groove insaid sheave. a recess from said sheave to an inside end sur face of saidmounting portion through which said cord is free to move. a nubprotruding slightly from a surface of said portion adjacent an interiorsurface of said body making contact with said surface which preventssaid pulley block unit from sliding out of said channel unless pulledtherefrom, and a pair of sheaves each rotatably mounted on one of saidspindles and having a protruding hub on at least one side of said sheavepreventing the movement of said sheave axially along said spindle.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIONPATENT NO. 3,892,041

DATED July 1, 1975 INVENTOR(S) Willaim A. Adair, and Richard F. PollowyIt is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 1, Line 37 delete "to" and insert or in place thereof.

Signal and Scaled this twenty-eight Day of October 1975 [SEAL] A ttest:

C. MARSHALL DANN ('vmmissimrvr njlaremx and Trarlvmurks RUTH C. MASONArresting Officer

1. In a straight edge assembly for cord mounting on a drafting board theimprovement comprising a permanently assembled body including an edgeproviding portion and a grasping portion, and a pulley block unitlocated at each end of said assembly which is manually removable andreplaceable without the use of tools, each said pulley block unitincluding an integrally formed pulley block and at least one sheavemounted therein, said block having an end cap portion for covering atleast a part of the end of said body, a sheave mounting portion adjacentsaid end cap portion including a spindle on which said sheave is mountedand retained in place by said contiguous body part, a recess throughwhich said mounting cord passes, and means for frictionally retainingeach said pulley block unit to a contiguous body part at the end of saidassembly and allowing releasable sliding engagement therebetweenincluding a nub extending from an outside surface of said portion whichfrictionally engages said contiguous body part.
 2. The improvement ofclaim 1 wherein said end cap portion further comprises, gripping meansthereon to facilitate removal thereof from said body portion, a shoulderat the juncture of said end cap and said sheave mounting portions, saidshoulder having the outer dimensions of said body adjacent thereto andinner dimensions of said sheave mounting portion and said end capportion having at least one passageway therein for traversal of amounting cord therethrough.
 3. In a straight edge assembly for mountingon a drafting board by a cord fastened mediate its ends to said board,said assembly including a body having an edge portion and adownwardly-facing C-channel shaped grasping portion the free ends ofwhich channel are permanently attached to said edge portion, theimprovement comprising, an integrally formed pulley block unit locatedat and partly inside each end of said body which is manually removableand replaceable without the use of tools, each said pulley block unitincluding an end cap portion, a sheave mounting portion attachedthereto, and a pair of sheaves mounted side by side therein, said endcap portion having outside dimensions corresponding approximately to thecross sectional outside dimensions of said grasping portion, grippingmeans for facilitating lateral manual removal of said unit from saidassembly, a pair of passageways therein for the traversal of said cordtherethrough, and a shoulder at the juncture of said marginal portionand said sheave mountiNg portion having the outside dimensions of saidbody adjacent thereto and the inside dimensions of said sheave mountingportion, said shoulder limiting the travel of said pulley block unit insaid body channel, said sheave mounting portion having outside crosssectional dimensions not appreciably greater than the correspondinginside dimensions of said channel in said body and frictionally retainedtherein, a pair of spindles each having a sheave rotatably mountedthereon, said spindles being retained in place by said contiguous bodypart, a cord retaining shoulder on said mounting portion around saidsheave preventing said cord from disengaging a groove in said sheave, arecess from said sheave to an inside end surface of said mountingportion through which said cord is free to move, a nub protrudingslightly from a surface of said portion adjacent an interior surface ofsaid body making contact with said surface which prevents said pulleyblock unit from sliding out of said channel unless pulled therefrom, anda pair of sheaves each rotatably mounted on one of said spindles andhaving a protruding hub on at least one side of said sheave preventingthe movement of said sheave axially along said spindle.